After a bit of digging the cylinder heads are diff. the caddy gets 2 (1.425in) intake valves same as the gxp but the caddy gets 2 (1.42 in) exhaust valves while the gxp only gets 2 (1.102 in) exhaust valves.
Also cadilac has a cam shaft posistion actuator system that allows the ecm to adjust cam shaft timming of all 4 cams while the engine is running, not the gxp.

I would think these two facts might add up to the 25hp drop in the gxp?

I thought only the new RWD northstar applications got the variable cam phasing version of the engine?

Scott may want to consider developing products that work with both fwd and rwd/awd applications - given caddy'* new performance image and success. The RWD northstar is in the new XLR roadster, SRX cross-over, and forthcoming 05 STS. I believe caddy is going to offer a supercharged version is the "v-series" of all these cars.

When is GM going to wise-up and start putting the 320 HP Caddy North* motor and tranny in the Bonneville GXP??,.....seems to me that GM Pontiac better start keeping pace with the rest of the recent Caddy HP upgrades if they want to keep GXP buyers still interested,....besides,what GXP owner wants to be totally blown-off by some fat-cat driving a hemi 300C??

Lets see... what happens when you drop a 320 horse motor in a front-wheel drive car? The 300C driver would be consoled by the sight of the Bonneville that beat him torque-steering into the weeds. Unless Pontiac made a trick drive system like Honda'* SH-AWD. Unlikely on a platform about to be discontinued Those bean-counting bastards! "Unless you're willing to spend money,you're pretty likely not to make any "

next-gen car
AWD or rear-drive
Ls2 390 hp.
6speed auto or manumatic
slick styling
under $45,000
Seeing the end of the 300C -priceless

Lets see... what happens when you drop a 320 horse motor in a front-wheel drive car? The 300C driver would be consoled by the sight of the Bonneville that beat him torque-steering into the weeds. Unless Pontiac made a trick drive system like Honda'* SH-AWD. Unlikely on a platform about to be discontinued Those bean-counting bastards! "Unless you're willing to spend money,you're pretty likely not to make any "

next-gen car
AWD or rear-drive
Ls2 390 hp.
6speed auto or manumatic
slick styling
under $45,000
Seeing the end of the 300C -priceless

Torque-steer is not problem with my GXP. In the newer grand prix with the 5.3 its a different story.